Actinic radiation curable compositions including semiconductor metal oxide materials

ABSTRACT

Described herein are inks and coating compositions comprising semiconductor metal oxides and composites thereof, which are natural environmentally sustainable materials that may be recycled and/or reused indefinitely. Semiconductor metal oxides offer an alternative to relatively more toxic, non-sustainable, photo and heat-degrading, migrating traditional photoinitiator agents used in actinic radiation curable compositions. The semiconductor metal oxides and composites thereof absorb visible or UV-light as photocatalysts and/or semiconductors, or absorb electron beam radiation, forming radicals for radical events as polymerization reactions and color enhancement events.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a § 371 National Phase application based onPCT/US19/12849 filed Jan. 9, 2020, which claims the benefit of U.S.Provisional Application Nos. 62/669,533, filed May 10, 2018 and62/740,996, filed Oct. 4, 2018 the subject matter of each of which isincorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention is directed to actinic radiation curablecompositions which undergo free radical polymerizations upon exposure toactinic radiation, such as the emission of a UV light source. Thecompositions include semiconductor metal oxide materials that initiatecuring and improve the color of the compositions. The semiconductormetal oxide materials may provide a replacement for all or part of thephotoinitiator materials that may be present in actinic radiationcurable compositions.

BACKGROUND

Actinic radiation curable compositions, such as inks, primers, coatingsand adhesives, are commonly employed in printing operations such asflexo, gravure, digital, among others. Such compositions includepolymerizable materials, such as ethylenically unsaturated monomers andoligomers, photoinitiators, colorants, inhibitors, waxes, etc. Thecompositions undergo curing when exposed to actinic radiation. Thecuring involves a free radical polymerization of the ethylenicallyunsaturated monomers and oligomers present in the compositions. Thephotoinitiators start a polymerization reaction when the composition isexposed to a reaction-starting dose of actinic radiation. The actinicradiation is emitted by an actinic light source, such as for exampleUV-light, which can be provided by a high- or medium-voltage mercurybulbs, a xenon bulb, a carbon arc lamp, a metal halide bulb, a LED lightsource (i.e., UV-LED lamp) and/or visible light, such as sunlight.Electron beam radiation may also be used to initiate curing of suchcompositions, in which case the compositions do not have to includephotoinitiators.

One of the problems that arise from the inclusion of photoinitiators inactinic radiation curable compositions is that after printing thecompositions onto substrates such as food packaging and then curingsame, photoinitiator residues may migrate out of the compositions overtime. Migratable residues may contaminate the goods packaged within theprinted packaging, which is particularly problematic if the goods arefoods, medicines, and the like. Further, migratable components maycontaminate the environment outside of the packaging. Manyphotoinitiators are classified as toxic materials, and thus they cannotbe included in compositions printed on items that come in direct contactwith food.

While high energy electron beam (E-beam or EB) curing may not requirethe presence of a photoinitiator, this curing method may not providefull and complete curing of ethylenically unsaturated monomers andoligomers. Thus, E-beam curing does not solve the problem ofmigratables.

It would be advantageous and beneficial to provide actinic radiationcurable compositions that are more eco-friendly, renewable, andenvironmentally sustainable.

References that may be of interest include:

U.S. Pat. Nos. 3,083,113, 4,959,297, 5,212,212, 6,267,949, 8,512,467 and8,623,220; U.S. Patent Appl. Publ. Nos. 2005/0153068, 2007/0259986,2008/0306201, 2010/0074837, 2012/0177928, 2014/0183141 and 2017/0216821;WO 2011/116972 and EP 2 368 919 A1;

The following non-patent literature documents:

-   Azan V, Lecamp L, Lebaudy P, Bunel C., Simulation of the    Photopolymerization Gradient Inside a Pigmented Coating—Influence of    TiO ₂ Concentration on the Gradient; Prog Org Coat 2007:58(1):70-75;-   Danu S, Darsono, Marsongko, UV-Curing of Titanium Dioxide Pigmented    Epoxy Acrylate Coating on Ceramic Tiles; Journal of the Ceramic    Society of Japan 2008:116(1356):896-903;-   J. A. Burunkova, I. Yu. Denisyuk, and S. A. Semina,    Self-Organization of ZnO Nanoparticles on UV-Curable Acrylate    Nanocomposites; Journal of Nanotechnology, vol. 2011, Article ID    951036, 6 pages, 2011. doi:10.1155/2011/951036;-   Nakayama, N. & Hayashi, T., Preparation and Characterization of    TiO—ZrO ₂ and Thiol-Acrylate Resin Nanocomposites with High    Refractive Index via UV-Induced Crosslinking Polymerization; Compos.    Part A 38, 1996-2004 (2007);-   Trouillas, P, et al., (2016), Stabilizing and Modulating Color by    Copigmentation: Insights from Theory and Experiment; Chem. Rev., 11;    116(9):4937-82.

SUMMARY OF THE INVENTION

Described herein are actinic radiation curable compositions, such asinks and coatings that are curable by exposure to actinic radiation. Thecompositions comprise a polymerizable component selected from anethylenically unsaturated monomer, an ethylenically unsaturatedprepolymer, and combinations thereof; and

a semiconductor metal oxide material, optionally present as a compositecomprising the semiconductor metal oxide material and another compositeforming material.

In one aspect, wherein the semiconductor metal oxide is as defined informula (I):M_(x)O_(y)H_(z)  (I)

-   -   wherein M is a metal selected from Ti, Zn, Mg, Ce, Bi, and Fe;        -   O is oxygen;    -   H is a halogen;    -   x is an integer of 1 to 3;    -   y is an integer of 1 to 3; and    -   z is an integer of 0 to 3.

Combinations of metal oxides as defined in formula (I) may be used.

In one aspect, the semiconductor metal oxide material is present as acomposite of the semiconductor metal oxide material and anothercomposite forming material selected from pigments, clays, humic acid,humic acid polymers, and photoactive substances that are capable ofresponding to light or electromagnetic radiation, such as opticalbrighteners and photoinitiators.

In one aspect, the semiconductor metal oxide semiconductor metal oxidematerial is present as a composite of the semiconductor metal oxidematerial and a pigment selected from carbon black, halloysite clays,aluminosilicate clays, magenta pigments such as lithol rubine pigments,and combinations thereof.

In one aspect, the semiconductor metal oxide material is present as acomposite of the semiconductor metal oxide material and anothercomposite forming material selected from carbon black, aluminosilicateclays and combinations thereof.

In one aspect, the polymerizable component comprises an ethylenicallyunsaturated material selected from one or more of an ethylenicallyunsaturated monomer and an ethylenically unsaturated prepolymer.

In one aspect, the ethylenically unsaturated prepolymer of thepolymerizable component is selected from epoxyacrylates, acrylated oils,urethane acrylates, polyester acrylates, polyether acrylates,vinyl/acrylic oligomers, polyene/thiol systems, and combinationsthereof.

In one aspect, the actinic radiation curable compositions furthercomprise one or more photoinitiators.

In one aspect, the actinic radiation curable compositions includephotoinitiators in lesser amounts than the amounts that are included inactinic radiation curable compositions that do not include thesemiconductor metal oxide materials described herein.

In one aspect, the actinic radiation curable compositions exhibitimproved color when compared to actinic radiation curable compositionsthat do not include the semiconductor metal oxide materials describedherein.

In one aspect, actinic radiation curable compositions are curable byexposure to sources of actinic radiation, such as, for example, visiblelight, such as sunlight, and UV-light. The UV-light for curing may beprovided by one or more of a high-voltage mercury bulb, a medium-voltagemercury bulb, a xenon bulb, a carbon arc lamp, a metal halide bulb, anda UV-LED light source.

In one aspect, the actinic radiation curable compositions are inks andcoatings suitable for application by process such as, for example,lithographic, flexographic, gravure, screen, spray, rod, spray, curtaincoater and digital.

As used in the present application the “semiconductor metal oxide” is amaterial that, in the presence of a polymerizable, ethylenicallyunsaturated component and when exposed to a reaction-starting dose ofactinic radiation, creates a free radical polymerization reactionpathway in the polymerizable, ethylenically unsaturated component, thecreation of the pathway being solely attributable to the metal oxide,and without loss of the semiconductor metal oxide during thephotopolymerization process. The activity is catalytic in that the metaloxide composite is not consumed and does not undergo an irreversiblechemical change and is available to assist with additional radicalreactions.

The initiation of a free radical polymerization reaction in thepolymerizable, ethylenically unsaturated component by the semiconductormetal oxide and which is solely attributable thereto can be demonstratedby a Differential Scanning calorimetry (DSC) plot of heat flow vs. timegenerated for a reaction system that has been exposed to areaction-starting dose of actinic radiation, wherein the reaction systemincludes an ethylenically unsaturated material and a semiconductor metaloxide material and whereby the system is free of photoinitiators (i.e.,not including photoinitiators), wherein the DSC plot shows thegeneration of heat (i.e., heat flow) indicative of a free radicalpolymerization reaction that is or has taken place in the system.

Photo DSCs are acquired using a TA DSC Q2000 w/TA PCA (PhotocalorimeterAccessory) Accessory w/012-64000 Hg Lamp. The pans used are T ZeroAluminum pans with one bare pan as the reference pan and a sample panthat contains between 10-15 mg of either the non-photoreactive orphotoreactive system. The sample and reference pans are irradiated withlight for 0.5 seconds to 2 seconds with the remainder of a 60 secondinterval being well time over the course of 10 total irradiation cycles.The lamp intensity may be set for 1% to 5% (2.0 W to 10 W) and at atemperature of 25° C. (isothermal). The PCA Accessory contains a 200 WHg High Vapor Pressure Lamp with a spectral output of 320 to 500 nm. Toevaluate the photoactivity of a BGA, the enthalpy (J/g) of the systemper cycle compared to a baseline monomer system was considered. In thiscase, monomers serve as the baseline and monomer blended with BGA as thephotoreactive system.

An Example of a DSC plot is provided herewith as the FIGURE anddemonstrates enhanced curing activity for a composite of a semiconductorTiO₂ metal oxide and carbon black (BGA1) in 1,6-hexanediol diacrylatewithout a photoinitiator being present. The activity is catalytic inthat the metal oxide composite is not consumed and does not undergo anirreversible chemical change and is available to assist with additionalradical reactions.

The above definition does not exclude the inventive actinic radiationcurable compositions described herein that include semiconductor metaloxide materials and one or more photoinitiators. In such compositions,the photoinitiators initiate curing upon actinic radiation exposure.

It has been found that actinic radiation curable compositions,optionally including photoinitiators, and semiconductor metal oxidesundergo a more complete and thorough cure than compositions that containonly photoinitiators. Also, compositions including photoinitiators andsemiconductor metal oxides exhibit improved color properties aftercuring. Such properties include improved color appearance, density, andgloss, which improvements are measurable. The cure and colorimprovements are demonstrated in the examples that follow.

As best understood, and not wishing to be bound by any theory, reactionpathway creation as mentioned in the above definition is not theinitiation of a free radical polymerization in the manner that organicphotoinitiators initiate free radical photopolymerization.

It should further be understood that the actinic radiation curablecomposition described herein can be cured by energy from an electronbeam apparatus (E-beam). In such instances, photoinitiator componentsmay not be present in the compositions. As shown in the examples thatfollow, inks and coatings that include the semiconductor metal oxidesexhibit improved curing when they include the semiconductor metaloxides.

The described actinic radiation curable inks and coating compositionsare more environmentally friendly than compositions that rely solely onphotoinitiator to initiate curing. The semiconductor metal oxidematerials contained in the inks and coating compositions operateaccording to green-technology principles (e.g., photocatalysis andradiation enhancement). The semiconductor metal oxide materials(considered to be metal oxide semiconductor materials) are renewable andsustainable. By including the semiconductor metal oxide materials (andcomposites thereof) in the actinic radiation curable compositions, theamounts and concentrations of traditional photoinitiators can bereduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE is a Photo-DSC spectrum demonstrating photocatalytic activityof a composite of a semiconductor TiO₂ metal oxide and carbon black(BGA1) in a reaction system containing the composite, 1,6-hexanedioldiacrylate (HDDA) monomer, and no photoinitiator. On exposure toUV-energy, a polymerization reaction is initiated in the HDDA. Thephotocatalytic activity is attributable to the composite since nophotoinitiator is present in the reaction system. The FIGURE also showsthat that there is no photocatalytic activity in a system that containsonly HDDA. Exposure conditions: UV-energy emitted at 0.5 second exposuretime and at 2% light intensity.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “ethoxylated” refers to chain extendedcompounds that include ethylene oxide as the chain extender.

“Propoxylated” refers to chain extended compounds that include propyleneoxide as the chain extender.

“Alkoxylated” refers to chain extended compounds that include ethyleneoxide and propylene oxide as chain extenders.

A “prepolymer” is an oligomer or other macromolecule that is capable offurther polymerization.

The actinic radiation curable inks and coatings include semiconductormetal oxide materials that are solid species capable of non-covalent,self-assembly interactions and are less likely to migrate out of thecured compositions than traditional molecular photoinitiators and theirresidues. Further, supramolecular complexes form between semiconductormetal oxide materials themselves and with a variety of hydrophobic orhydrophilic species.

Semiconductor metal oxide material form excited state electron-holepairs (excitons) exhibiting quantum confinement properties affectingexcited state electron hole pairs. It is well known that this propertyvaries from semiconductor to semiconductor and is influenced by thetreatments performed on semiconductor metal oxides. An exciton is abound state of an electron and an electron hole that are attracted toeach other by the electrostatic Coulomb force. Excitons form uponradiation absorption by the semiconductor metal oxide material. It is anelectrically neutral quasiparticle that exists in insulators,semiconductor metal oxide materials and in some liquids. The exciton isregarded as an elementary excitation of condensed matter that cantransport energy without transporting net electric charge. Excitons formwhen a photon is absorbed by a semiconductor material, such as thesemiconductor metal oxide materials (and composites thereof) that areused herein. A photon excites an electron from the valence band into theconduction band in the semiconductor. In turn, this leaves behind apositively charged electron hole (an abstraction for the location fromwhich an electron was moved). The electron in the conduction band isthen effectively attracted to this localized hole by the repulsiveCoulomb forces from large numbers of electrons surrounding the hole andexcited electron. This attraction provides a stabilizing energy balance.Consequently, the exciton has slightly less energy than the unboundelectron and hole. The wave function of the bound state is said to be‘hydrogenic’, an exotic atom state akin to that of a hydrogen atom(except for the zero rest mass of the hole). The binding energy is muchsmaller and particle size is much larger than a hydrogen atom. This isbecause of both the screening of the Coulomb force by other electrons inthe semiconductor (i.e., its dielectric constant), and the smalleffective masses of the excited electron and hole. The recombination ofthe electron and hole, i.e. the decay of the exciton, is limited byresonance stabilization due to the overlap of the electron and hole wavefunctions, resulting in an extended lifetime for the exciton.

The lifetimes of photogenerated electrons and holes (reductive/oxidativecenters) are increased. In the case of actinic radiation curablecompositions, the possibility exists for exchange between thesemiconductor metal oxide radical species and charge with monomeracrylates near the photocatalyst surface. These photo-induced eventsinitiate photochemical curing reactions. The occurrence of interfacialelectron transfer, i.e., transfer of an electron to or from a substrateadsorbed onto the light-activated semiconductor takes place inphotocatalytic processes, and the efficiency thereof effects the abilityof the semiconductor to serve as a photocatalyst for a given redoxreaction. The efficiency of electron transfer reactions is, in turn, afunction of the position of the semiconductor's conduction and valenceband-edges relative to the redox potentials of the adsorbed acrylatemonomer moieties.

Advantageously and beneficially, the described actinic radiation curablecompositions are more eco-friendly, renewable and environmentallysustainable than traditional photoinitiators used to initiatephoto-polymerization. The actinic radiation curable compositions includelower concentrations of relatively toxic traditional photoinitiators andprovide a lessened possibility of the migration of partially-reactedmonomers/oligomers and photoinitiators into surrounding environment andmaterials.

The semiconductor metal oxide materials and composites thereof describedherein initiate photocatalytic curing in the ethylenically unsaturatedmaterials included in the described actinic radiation curablecompositions. Further, it has been found that the inclusion to thesemiconductor metal oxide materials results in the enhancement of colorin the compositions. Thus, they further act as color enhancing agents.By including the semiconductor metal oxide materials, a lesser amount ofphotoinitiator material may be included in the compositions whencompared to the amount of photoinitiator material included incompositions that do not include the semiconductor metal oxide materialsand composites thereof. As a result thereof, the amount of potentialmigratable components, which may include toxic byproducts, is reduced.The complexes that form are stable, ecofriendly and offer facilemolecular-architecture modification towards a many differentsophisticated supramolecular composites with varying UV absorbanceactivity and functionality (nanotechnology). Composites includecomplexes with natural carbon black moieties and oxidized natural humicacid polymers.

The semiconductor metal oxide materials are semiconductor materials thatdo not degrade in performing as initiators of curing events uponexposure to actinic radiation since they act as catalysts during curingand do not act as reactants.

Further, government regulations have indirectly initiated efforts tofind more environmentally friendly and safer alternatives to theinclusion of photoinitiators in actinic radiation curable compositions.The described actinically curable inks and coating compositions provideeco-friendly and safer alternatives to photoinitiators, since theamounts of photoinitiators can be eliminated or lessened in theactinically curable composition.

The above-mentioned color-improving property of the semiconductor metaloxide materials is a new and unexpected property not exhibited bytraditional photoinitiators.

The semiconductor metal oxide materials and composites are superior totraditional photoinitiators for reasons including: they do not degradeover time (typical photoinitiators are relatively unstable and haveshorter shelf-lives under varying conditions of temperature and oxygen)and are not known to form toxic side products upon exposure to UV lightenergy.

In addition, composites of the semiconductor metal oxide materialsincluded in the presently described actinic radiation curablecompositions can readily incorporate other components that aid inimproving the cure and the color of the compositions. One benefit of acomposite is that it may attract and bind reactive ethylenicallyunsaturated materials such as acrylate monomers to the reaction surfaceof the semiconductor metal oxide through non-covalent interactions. Thiscould take place with composites of semiconductor metal oxide and carbonblack. One such composite is BGA1—a composite of semiconductor TiO₂metal oxide and carbon black, described in the examples that follow.

Unlike traditional photoinitiators, the UV absorbance band of thesemiconductor metal oxide materials used in the present actinicradiation curable composition can be adjusted towards desiredwavelengths of the UV spectrum, thereby improving the curing activity inthe compositions when exposed to curing energy. In addition, because ofthe dual concurrent photo-induced oxidation/reduction actions at thesurface of semiconductor metal oxide material-based composites, thecomposites may be used in antimicrobial/anti-odor applications(oxidation/reduction of microbes); multiple free radical generationduring curing; photovoltaic applications; and/or water remediation.

The semiconductor metal oxide materials and composites thereof areenvironmentally sustainable materials and may also be repurposed fromused materials and be reused indefinitely. The semiconductor metal oxidematerials and composites thereof offer dual (reductive and oxidative)free radical generation for curing mechanisms, and the composites may bedesigned with molecular scaffolding. For example, supportive molecularstructures such as carbon black, clay, and other additives can interactwith semiconductor metal oxide materials and ethylenically unsaturatedmaterials such as monomers, oligomers and prepolymers for more efficientcuring reactions. Additionally, the composites may also interact withpigments to promote color properties as well as curing reactions.Composites modified with pigments can be added singularly toformulations and improve cure and color development. Further, thepigment-modified composites can be exposed to visible light to achieveimprovement in color. Alternatively, semiconductor metal oxide materialsand composites thereof may interact directly with semiconductor metaloxides, monomers, and pigments, without the need for supportivemolecular scaffolding, to enhance cure and color directly.

In one aspect, the described semiconductor metal oxide materials andcomposites thereof include a semiconductor metal oxide defined informula (I) as:M_(x)O_(y)H_(z)  (I)

-   -   wherein M is a metal selected from Ti, Zn, Mg, Ce, Bi, and Fe;    -   O is oxygen;    -   H is a halogen;    -   x is an integer of 1 to 3;    -   y is an integer of 1 to 3; and    -   z is an integer of 0 to 3.    -   Combinations of metal oxides as defined in formula (I) may be        used.

Among the semiconductor metal oxide materials and composites thereofthat may be included in the present actinic radiation curablecompositions are photoactive nanocomposite anatase-TiO₂, ZnO, and otherphotocatalytic band gap semiconductors. These materials effect and/oraugment cure and enhance the color of the cured compositions Further,semiconductor metal oxide materials and composites thereof aredemonstrated to increase the optical density and improve the ‘jetness’of compositions containing black pigments, without experiencingdecreased curing efficiency. Further, curing occurs effectively in avariety of actinic radiation curable compositions, including thosecontaining lesser amounts of photoinitiator. The semiconductor metaloxide materials and composites thereof are less toxic and more stablethan traditional photoinitiators. They can be stored over longer timeperiods, have better shelf-life and are more heat and light resistantthan traditional photoinitiators. Further, the semiconductor metal oxidematerials and composites thereof have been shown to work synergisticallyalone and as composites with certain additives such as carbon black.

Semiconductor metal oxide materials and composites thereof are morestable (i.e., do not degrade) and are less likely to migrate even afterexposed to UV light, when compared to typical photoinitiator packages.Semiconductor metal oxide materials and composites thereof are furtheradvantageous in that their photocatalytic properties involve dualphoto-induced oxidative/reductive free radical curing pathways. Anadvantageous property possessed by band gap additives such as thesemiconductor metal oxide materials are the dual oxidation/reductivefree radical promoting pathways that they work along when aiding curing.A photocatalyst, such as a semiconductor metal oxide material, undergoeselectronic excitation upon exposure to UV radiation from its valenceband to its conduction band. This results in the simultaneous generationof a reducing-agent free electron and an oxidative hole that drive freeradical curing reactions. In the process, the photocatalyst loseselectronic excitation energy and gains a valence bond electron and isthen ready for another UV excitation event. Thus, the photocatalyst doesnot degrade with UV light and may generate curing reactions multipletimes. In addition, the presence of water or oxygen will not inhibit thecuring activity of the metal oxide photoinitiator.

The stability and supramolecular adaptability of semiconductor metaloxide materials allow them to be combined into a variety of compositeswith varying UV absorbance or radiation enhancing activity. Notably,semiconductor metal oxides may also form supramolecular complexes andcomposites with pigments, enhancing color and cure.

Semiconductor metal oxide materials are semiconductors that may also actas radiation enhancers. That is, if these semiconductor materials areexposed to high energy subatomic particles, such as emitted by anelectron beam, electron reduction into band gap/conduction band andAuger electron effects induce electron emission amplification, therebycausing the semiconductor metal oxides to act as radiation enhancers.Semiconductor metal oxide materials exposed to an electron beam willemit further electrons which increase free radical curing reactions.

The invention described herein makes use of semiconductor metal oxidematerials and composites thereof that function as semiconductors, whichshare several advantages over conventional photoinitiator packages.Semiconductor metal oxide materials are not adversely affected by heat,unlike traditional photoinitiators. The semiconductor metal oxidematerials may be utilized alone, or as composites within actinicradiation curable compositions. In all cases, the materials offer dualreduction/oxidation pathways that create monomer free radicals, whichaid photochemical curing and are not affected by oxygen inhibitioninteractions. In addition, the chemical structure of semiconductor metaloxide materials offers opportunities to design and create non-covalentsupramolecular scaffolding with a composite material such as carbonblack that can adsorb reactive monomer/oligomer species near thesemiconductor metal oxides photoactive surface, thereby enhancingreaction efficiency.

Some other advantages:

The semiconductor metal oxide materials and composites thereof providerenewable, sustainable, eco-friendly and do not photodegrade with use;

The semiconductor metal oxide materials and composites thereof arepreferably solid state composites that are less likely to migrate andare suitable for food packaging;

The semiconductor metal oxide materials and composites thereof can beused as a replacement for all or part of the amount of traditional, moretoxic photoinitiators that are included in actinic radiation curablecompositions, thus lowering the amounts of the photoinitiators;

The semiconductor metal oxide materials and composites thereof can worksynergistically with photoinitiators, and in combination therewith, toenhance UV curing effects;

The wavelength absorbance of the semiconductor metal oxide materials maybe modified using a variety of composite additives;

The semiconductor metal oxide materials and composites thereof arecompatible in a variety of actinic radiation curable compositions; and

Actinically cured compositions including the semiconductor metal oxidematerials and composites thereof provide improved chemical resistance,cure, color density and gloss.

Composites of the semiconductor metal oxide materials compositions ofthe present embodiment include the semiconductor metal oxide materialand additives including, for example but not limited to: clays, such ashalloysites and aluminosilicates; H₂O; carbon black; acrylate monomers;humic acid, humic acid polymers, dyes and pigments to enhance UVcuring/color, and photoactive substances that are capable of respondingto light or electromagnetic radiation, such as optical brighteners andphotoinitiators.

The applicants have found that a TiO₂ pigment available under the tradename Altiris 550 and available from Huntsman is an effectivesemiconductor metal oxide material for use as a curing aid in an actinicradiation curable composition, such as an ink or coating compositionsthat will be cured by exposure to UV light. The inclusion of thissemiconductor metal oxide material enables the reduction of the amountof traditional photoinitiators that would otherwise be included in anenergy curable ink formulation. Further, the properties of the ink andcoating compositions that includes this semiconductor metal oxidematerial is comparable to or is improved relative to ink and coatingcompositions that do not include same.

There are other advantages that flow from the inclusion ofsemiconductive TiO₂ metal oxide such as Altiris 550 in the presentactinic radiation curable compositions. Among them are: reduced amountsof migratable components, due to the inclusion of a reduced amount ofphotoinitiator, a benefit of particular relevance for printing packagingfor foods and other sensitive items (e.g., over-the-counter andprescription medicines); compatibility in hydrophobic and hydrophiliccompositions; compliance with Nestle and Swiss ordinances, as well asregulatory schemes of other government agencies; and can be suitablyincluded in inks and coatings applied by virtually all printing methods,e.g., flexo, litho, gravure, LED flexo, ink jet and screen inksproducts.

It should be understood that not all metal oxides are semiconductiveand/or photocatalytic materials. Many metal oxides will not perform assemiconductors, and thus will not initiate a free-radical polymerizationreaction when in the presence of an ethylenically unsaturated materialand exposed to actinic radiation. For example, a DSC for such a systemincluding an ethylenically unsaturated material (e.g., 1,6-HDDA) and anon-semiconductive metal oxide material or composite thereof (e.g.,BGA1, described later herein, in which the semiconductive TiO₂ isreplaced with a non-semiconductive TiO₂) would not show generation ofheat of reaction, indicating that free radical polymerization has notoccurred, which demonstrates that this particular TiO₂ is not asemiconductive metal oxide material.

Table 1 below identifies exemplary metal oxide materials that exhibitsemiconductive and/or photocatalytic effect, additives that may be usedto make composites of the semiconductor metal oxide materials, andexemplary composites of semiconductor metal oxide materials andadditives. The information provided in Table 1 is exemplary and notlimiting in any way.

While not wishing to be limited by numerical limitations, it isgenerally known that TiO₂ materials used as pigments in inkcompositions, which do not display the semiconductive properties ofsemiconductive metal oxides as defined and described herein, haveparticle sizes of 250 nm or greater. On the other hand, TiO₂ materialshaving particle sizes of 1 nm to 200 nm, or 1 nm to 175 nm, or 1 nm to150 nm, or 1 nm to 120 nm, have been found to be semiconductive. Itshould be noted that these numeric ranges does not necessarily applyuniversally, as for example, the Altiris 550 TiO₂ semiconductive metaloxide described herein is not believed to conform to this comment onparticle size.

Composites of the semiconductor metal oxide materials may beparticularly well suited for inclusion in the actinic radiation curablecompositions described herein. As indicated above, the additivesincluded in the composites may tune and adjust the band gap of thesemiconductor metal oxide material, thereby providing maximizedphotocatalytic activity and the wavelengths of light used to cure thecompositions. Among those materials are pigments, clays, humic acid,humic acid polymers, photoactive substances that are capable ofresponding to light or electromagnetic radiation, such as opticalbrighteners and photoinitiators.

In one aspect, the semiconductor metal oxide material is present as acomposite of the semiconductor metal oxide material and a pigmentselected from carbon black, halloysite clays, and aluminosilicate clays,magenta pigments such as lithol rubine pigments, and combinationsthereof.

In one aspect, the semiconductor metal oxide material is present as acomposite of the semiconductor metal oxide material and anothercomposite forming material selected from carbon black, aluminosilicateclay, and combinations thereof.

As indicated, one advantage of the present invention is that the amountof photoinitiator can be lessened by the inclusion of the semiconductormetal oxide material and composites thereof. For example, it is has beenfound that the semiconductor metal oxide material and composites thereofcan replace all or part of the photoinitiator typically included in theactinic radiation curable compositions on a 1 to 1 (w/w/) basis, basedon the total weight of the composition.

In one aspect, the semiconductor metal oxide material (and/or compositethereof) is present in an amount of 0.1 wt % to 25 wt %, preferably 0.5wt % to 20 wt %, more preferably 1.0 wt % to 10 wt %, based on the totalweight of the composition.

Composites may be formed by mixing the components for a sufficientperiod of time on DAC speed mixers and/or on ultrasonic processors suchas sonicators.

Polymerizable Component

In one aspect, the polymerizable component is present in the actinicradiation curable compositions in an amount of 10 wt % to 90 wt %,preferably 60 wt % to 90 wt %, more preferably 70 wt % to 90 wt %, basedon the total weight of the composition.

Many different species of monofunctional and multifunctionalethylenically unsaturated materials may be used in the present actinicradiation curable compositions. A merely exemplary and non-exclusivelist of same includes:

Monofunctional Ethylenically Unsaturated Monomers

Examples of suitable monofunctional ethylenically unsaturated monomersinclude but are not limited to the following:

isobutyl acrylate; cyclohexyl acrylate; iso-octyl acrylate; n-octylacrylate; isodecyl acrylate; iso-nonyl acrylate; octyl/decyl acrylate;lauryl acrylate; 2-propyl heptyl acrylate; tridecyl acrylate; hexadecylacrylate; stearyl acrylate; iso-stearyl acrylate; behenyl acrylate;tetrahydrofurfuryl acrylate; 4-t.butyl cyclohexyl acrylate;3,3,5-trimethylcyclohexane acrylate; isobornyl acrylate; dicyclopentylacrylate; dihydrodicyclopentadienyl acrylate; dicyclopentenyloxyethylacrylate; dicyclopentanyl acrylate; benzyl acrylate; phenoxyethylacrylate; 2-hydroxy-3-phenoxypropyl acrylate; alkoxylated nonylphenolacrylate; cumyl phenoxyethyl acrylate; cyclic trimethylolpropane formalacrylate; 2(2-ethoxyethoxy) ethyl acrylate; polyethylene glycolmonoacrylate; polypropylene glycol monoacrylate; caprolactone acrylate;ethoxylated methoxy polyethylene glycol acrylate; methoxy triethyleneglycol acrylate; tripropyleneglycol monomethyl ether acrylate;diethylenglycol butyl ether acrylate; alkoxylated tetrahydrofurfurylacrylate; ethoxylated ethyl hexyl acrylate; alkoxylated phenol acrylate;ethoxylated phenol acrylate; ethoxylated nonyl phenol acrylate;propoxylated nonyl phenol acrylate; polyethylene glycol o-phenyl phenylether acrylate; ethoxylated p-cumyl phenol acrylate; ethoxylated nonylphenol acrylate; alkoxylated lauryl acrylate; ethoxylatedtristyrylphenol acrylate; N-(acryloyloxyethyl)hexahydrophthalimide;N-butyl 1,2 (acryloyloxy) ethyl carbamate; acryloyl oxyethyl hydrogensuccinate; octoxypolyethylene glycol acrylate; octafluoropentylacrylate; 2-isocyanato ethyl acrylate; acetoacetoxy ethyl acrylate;2-methoxyethyl acrylate; dimethyl aminoethyl acrylate; 2-carboxyethylacrylate; 4-hydroxy butyl acrylate, and combinations thereof.Methacrylate counterpart compounds to the above may also be included(e.g., isobutyl methacrylate to isobutyl acrylate), although thoseskilled in the art will appreciate that methacrylate compounds havelower reactivity than their equivalent acrylate counterparts.

Examples of suitable multifunctional ethylenically unsaturated monomersinclude but are not limited to the following: 1,3-butylene glycoldiacrylate; 1,4-butanediol diacrylate; neopentyl glycol diacrylate;ethoxylated neopentyl glycol diacrylate; propoxylated neopentyl glycoldiacrylate; 2-methyl-1,3-propanediyl ethoxy acrylate;2-methyl-1,3-propanediol diacrylate; ethoxylated2-methyl-1,3-propanediol diacrylate; 3 methyl 1,5-pentanedioldiacrylate; 2-butyl-2-ethyl-1,3-propanediol diacrylate; 1,6-hexanedioldiacrylate; alkoxylated hexanediol diacrylate; ethoxylated hexanedioldiacrylate; propoxylated hexanediol diacrylate; 1,9-nonanedioldiacrylate; 1,10 decanediol diacrylate; ethoxylated hexanedioldiacrylate; alkoxylated hexanediol diacrylate; diethyleneglycoldiacrylate; triethylene glycol diacrylate; tetraethylene glycoldiacrylate; polyethylene glycol diacrylate; propoxylated ethylene glycoldiacrylate; dipropylene glycol diacrylate; tripropyleneglycoldiacrylate; polypropylene glycol diacrylate; poly (tetramethyleneglycol) diacrylate; cyclohexane dimethanol diacrylate; ethoxylatedcyclohexane dimethanol diacrylate; alkoxylated cyclohexane dimethanoldiacrylate; polybutadiene diacrylate; hydroxypivalyl hydroxypivalatediacrylate; tricyclodecanedimethanol diacrylate;1,4-butanediylbis[oxy(2-hydroxy-3,1-propanediyl)]diacrylate; ethoxylatedbisphenol A diacrylate; propoxylated bisphenol A diacrylate;propoxylated ethoxylated bisphenol A diacrylate; ethoxylated bisphenol Fdiacrylate; 2-(2-vinyloxyethoxy)ethyl acrylate; dioxane glycoldiacrylate; ethoxylated glycerol triacrylate; glycerol propoxylatetriacrylate; pentaerythritol triacrylate; trimethylolpropanetriacrylate; caprolactone modified trimethylol propane triacrylate;ethoxylated trimethylolpropane triacrylate; propoxylated trimethylolpropane triacrylate; tris (2-hydroxy ethyl) isocyanurate triacrylate;e-caprolactone modified tris (2-hydroxy ethyl) isocyanurate triacrylate;melamine acrylate oligomer; pentaerythritol tetraacrylate; ethoxylatedpentaerythritol tetraacrylate; di-trimethylolpropane tetra acrylate;dipentaerythritol pentaaacrylate; dipentaerythritol hexaacrylate;ethoxylated dipentaerythritol hexaacrylate, and combinations thereof.Methacrylate counterpart compounds to the above may also be included(e.g., isobutyl methacrylate to isobutyl acrylate), although thoseskilled in the art will appreciate that methacrylate compounds havelower reactivity than their equivalent acrylate counterparts.

Other functional monomer species and classes capable of being used inpart in these formulations include cyclic lactam such as N-vinylcaprolactam; N-vinyl oxazolidinone and N-vinyl pyrrolidone, andsecondary or tertiary acrylamides such as acryloyl morpholine; diacetoneacrylamide; N-methyl acrylamide; N-ethyl acrylamide; N-isopropylacrylamide; N-t.butyl acrylamide; N-hexyl acrylamide; N-cyclohexylacrylamide; N-octyl acrylamide; N-t.octyl acrylamide; N-dodecylacrylamide; N-benzyl acrylamide; N-(hydroxymethyl)acrylamide;N-isobutoxymethyl acrylamide; N-butoxymethyl acrylamide; N,N-dimethylacrylamide; N,N-diethyl acrylamide; N,N-propyl acrylamide; N,N-dibutylacrylamide; N,N-dihexyl acrylamide; N,N-dimethylamino methyl acrylamide;N,N-dimethylamino ethyl acrylamide; N,N-dimethylamino propyl acrylamide;N,N-dimethylamino hexyl acrylamide; N,N-diethylamino methyl acrylamide;N,N-diethylamino ethyl acrylamide; N,N-diethylamino propyl acrylamide;N,N-dimethylamino hexyl acrylamide; and N,N′-methylenebisacrylamide.

Combinations of any of the above may be used in the presentcompositions.

Ethylenically Unsaturated Oligomers/Prepolymers

The at least one prepolymer consisting of an oligomer may preferably beselected from the group consisting of epoxy acrylates, acrylated oils,urethane acrylates (aliphatic and aromatic), polyester acrylates,polyether acrylates, vinyl/acrylic oligomers, polyene/thiol systems, andcombinations thereof

Photoinitiators

The present compositions may include one or more photoinitiators. In oneaspect, the photoinitiator component is present in the actinic radiationcurable compositions in an amount of 2.0 wt % to 40 wt %, preferably 5.0wt % to 25 wt %, more preferably 5.0 wt % to 20 wt %, based on the totalweight of the composition. In a further aspect, this amount is less thanthe amount of photoinitiator provided in an actinic radiation curablecomposition that does not include the described semiconductor metaloxide material and composites thereof.

The semiconductor metal oxide materials and composites thereof have beenfound to work together with photoinitiators to provide a fast, thoroughcure. Suitable photoinitiators include, but are not limited to, thefollowing: α-hydroxyketones such as; 1-hydroxy-cyclohexyl-phenyl-ketone;2-hydroxy-2-methyl-1-phenyl-1-propanone;2-hydroxy-2-methyl-4′-tert-butyl-propiophenone;2-hydroxy-4′-(2-hydroxyethoxy)-2-methyl-propiophenone;2-hydroxy-4′-(2-hydroxypropoxy)-2-methyl-propiophenone; oligo2-hydroxy-2-methyl-1-[4-(1-methyl-vinyl)phenyl]propanone;bis[4-(2-hydroxy-2-methylpropionyl)phenyl]methane;2-Hydroxy-1-[1-[4-(2-hydroxy-2-methylpropanoyl)phenyl]-1,3,3-trimethylindan-5-yl]-2-methylpropan-1-oneand2-Hydroxy-1-[4-[4-(2-hydroxy-2-methylpropanoyl)phenoxy]phenyl]-2-methylpropan-1-one;acylphosphine oxides such as; 2,4,6-trimethylbenzoyl-diphenylphosphineoxide; ethyl (2,4,6-trimethylbenzoyl)phenyl phosphinate; andbis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; α-aminoketones suchas; 2-methyl-1-[4-methylthio)phenyl]-2-morpholinopropan-1-one;2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one; and2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one;thioxanthones such as; 2-4-diethylthioxanthone, isopropylthioxanthone,2-chlorothioxanthone, and 1-chloro-4-propoxythioxanthone; benzophenonessuch as; such as benzophenone, 4-phenylbenzophenone, and4-methylbenzophenone; methyl-2-benzoylbenzoate;4-benzoyl-4-methyldiphenyl sulphide; 4-hydroxybenzophenone;2,4,6-trimethyl benzophenone, 4,4-bis(diethylamino)benzophenone;benzophenone-2-carboxy(tetraethoxy)acrylate; 4-hydroxybenzophenonelaurate and1-[-4-[benzoylphenylsulpho]phenyl]-2-methyl-2-(4-methylphenylsulphonyl)propan-1-one;phenylglyoxylates such as; phenyl glyoxylic acid methyl ester;oxy-phenyl-acetic acid 2-[hydroxyl-ethoxy]-ethyl ester, oroxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester;oxime esters such as;1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime; [1-(4-phenylsulfanylbenzoyl)heptylideneamino]benzoate, or[1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]-ethylideneamino]acetate;Examples of other suitable photoinitiators include diethoxyacetophenone; benzyl; benzyl dimethyl ketal; titanocen radicalinitiators such as titanium-bis(η5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl];9-fluorenone; camphorquinone; 2-ethyl anthraquinone; and the like.

Polymeric photoinitiators and sensitizers are also suitable, including,for example, polymeric aminobenzoates (GENOPOL AB-1 or AB-2 from RAHN,Omnipol ASA from IGM or Speedcure 7040 from Lambson), polymericbenzophenone derivatives (GENOPOL BP-1 or BP-2 from RAHN, Omnipol BP,Omnipol BP2702 or Omnipol 682 from IGM or Speedcure 7005 from Lambson),polymeric thioxanthone derivatives (GENOPOL TX-1 or TX-2 from RAHN,Omnipol TX from IGM or Speedcure 7010 from Lambson), polymericaminoalkylphenones such as Omnipol 910 from IGM; polymeric benzoylformate esters such as Omnipol 2712 from IGM; and the polymericsensitizer Omnipol SZ from IGM.

Irgacure®TPO is (2,4,6-trimethylbenzoyldiphenylphosphine oxide).Irgacure®TPO-L is (2,4,6-trimethylbenzoylphenyl phosphinate).Omnirad®907 is(2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one).Irgacure®TPO and Irgacure®TPO-L were previously known as Lucirin®TPO andLucirin®TPO-L, respectively. Omnirad®907 was previously known asIrgacure®907.

Combinations of one or more photoinitiators may be included in thecompositions.

Further, certain initiators are known to be toxic. The above-describedsemiconductive TiO₂ metal oxide material (among other semiconductormetal oxide materials) are potential replacements for photoinitiatorssuch as Irgacure® 369(2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1), which isknown to pose a risk to unborn children. In a preferred aspect of thepresent application, the actinic radiation curable compositions are freeof Irgacure® 369.

Other Components

The actinic radiation curable compositions may include other componentswhich perform one or more functions and/or provide one or moreattributes to the compositions. Among them are:

Amine Synergists

An amine synergist may also be included in the formulation. Suitableexamples include, but are not limited to, the following: Aromatic aminessuch as; 2-(dimethylamino)ethylbenzoate; N-phenyl glycine; benzoic acid,4-(dimethylamino)-, 1,1′-[(methylimino)di-2,1-ethanediyl] ester; andsimple alkyl esters of 4-(N,N-dimethylamino)benzoic acid, with ethyl,amyl, 2-butoxyethyl and 2-ethylhexyl esters being particularlypreferred; other positional isomers of N,N-dimethylamino)benzoic acidesters are also suitable.

Others that may be included are, for example, aliphatic amines such asN-methyldiethanolamine, triethanolamine and tri-isopropanolamine;Aminoacrylates and amine modified polyether acrylates Ebecryl 80,Ebecryl 81, Ebecryl 83, Ebecryl 85, Ebecryl 880, Ebecryl LEO 10551,Ebecryl LEO 10552, Ebecryl LEO 10553, Ebecryl 7100, Ebecryl P115 andEbecryl P116 available from ALLNEX; CN501, CN550, CN UVA421, CN3705,CN3715, CN3755, CN381 and CN386, all available from Sartomer; Genomer5142, Genomer 5161, Genomer 5271 and Genomer 5275 from Rahn; Photomer4771, Photomer 4967, Photomer 5006, Photomer 4775, Photomer 5662,Photomer 5850, Photomer 5930, and Photomer 4250 all available from IGM,Laromer LR8996, Laromer LR8869, Laromer LR8889, Laromer LR8997, LaromerPO 83F, Laromer PO 84F, Laromer PO 94F, Laromer PO 9067, Laromer PO9103, Laromer PO 9106 and Laromer P077F, all available from BASF; Agisyn701, Agisyn 702, Agisyn 703, NeoRad P-81 and NeoRad P-85 ex DSM-AGI.Combinations of any of the above may be included.

Colorants

Suitable colorants include, but are not limited, to organic or inorganicpigments and dyes. The dyes include but are not limited to fluorescentdyes, azo dyes, anthraquinone dyes, xanthene dyes, azine dyes,combinations thereof and the like. Organic pigments may be one pigmentor a combination of pigments, such as for instance Pigment YellowNumbers 12, 13, 14, 17, 74, 83, 114, 126, 127, 174, 188; Pigment RedNumbers 2, 22, 23, 48:1, 48:2, 52, 52:1, 53, 57:1, 112, 122, 166, 170,184, 202, 266, 269; Pigment Orange Numbers 5, 16, 34, 36; Pigment BlueNumbers 15, 15:3, 15:4; Pigment Violet Numbers 3, 23, 27; and/or PigmentGreen Number 7. Inorganic pigments may be one of the followingnon-limiting pigments: iron oxides, titanium dioxides, chromium oxides,ferric ammonium ferrocyanides, ferric oxide blacks, Pigment Black Number7 and/or Pigment White Numbers 6 and 7. Other organic and inorganicpigments and dyes can also be employed, as well as combinations thatachieve the colors desired.

The colorant employed in the present invention may be any FD&C or D&Cpigment. Preferred FD&C pigments include FD&C Red No. 40, FD&C YellowNo. 5, FD&C Yellow No. 6 and FD&C Blue No. 1. Preferred D&C pigmentsinclude D&C Red No. 6, D&C Red No. 7, D&C Red No. 21, D&C Red No. 22,D&C Red No. 27, Red No. 28, D&C Red No. 30, D&C Red No. 33, D&C Red No.34, D&C Red No. 36, D&C Orange No. 5 and D&C Yellow No. 10.

Optical Brighteners

The actinically curable composition may also include opticalbrighteners. Optical brighteners are known to be colorless orpale-colored organic compounds which absorb in the UV range and whichreemit most of the absorbed UV light as blue fluorescent light havingwavelengths of from 400 to 500 nm. Luminescence detectors emit UV lightand can detect the resulting fluorescent light. Examples of suitableoptical brighteners include distyrylbenzenes, distyrylbiphenyls,stilbene derivatives, such as divinylstilbenes, triazinylaminostilbenes,stilbenyl-2H-triazoles, stilbenyl-2H-naphtho[1,2-d]triazoles andbis(1,2,3-triazolyl)stilbenes, each of which may be further substituted.Further examples include benzoxazoles, stilbenylbenzoxazoles,bisbenzoxazoles, benzimidazole derivatives, pyrazoline derivatives orcoumarin derivatives. Optical brighteners are commercially available,for example under the names Blankophor®, Tinopal® or Ultraphor®.Mixtures of different optical brighteners may also be used. The amountof optical brighteners used is usually from 1.0 wt % to 25% by weight,based on the total weight of the composition.

Waxes

The actinically curable composition may also include waxes such as butnot limited to amide wax, erucamide wax, polypropylene wax, paraffinwax, polyethylene wax, TEFLON®, carnauba wax and the like. The wax maybe a combination of said waxes. It is preferred that the wax be a blendof amide and erucamide waxes. The wax, if present, is in an amount of 0wt % to 4.0 wt %. It is preferred that the wax be present in an amountfrom 0.1 wt % to 2.0 wt %.

Other Additives

As with most actinically curable composition, additives may beincorporated to enhance various properties. A partial list of suchadditives includes but is not limited to adhesion promoters, silicones,light stabilizers, de-gassing additives, ammonia, flow promoters,defoamers, antioxidants, stabilizers, surfactants, dispersants,plasticizers, rheological additives, waxes, silicones, etc.

Curing

The actinic radiation curable compositions of the present invention canbe cured by exposure to light emitted by an actinic light source, suchas for example visible light, such as sunlight, and UV-light, which maybe provided by a high-voltage mercury bulb, a medium-voltage mercurybulb, a xenon bulb, a carbon arc lamp, a metal halide bulb, and a UV-LEDlight source. The compositions may also be cured by exposure to electronbeam (EB) radiation.

The wavelength of the actinic irradiation applied to the compositions ispreferably within a range of about 200 to 500 nm, more preferably about250 to 390 nm. UV energy is preferably within a range of about 30 to3,000 mJ/cm², and more preferably within a range of about 50 to 500mJ/cm². In addition, the bulb or other source can be appropriatelyselected according to the absorption spectrum of the radiation curablecomposition. Moreover, the actinically curable composition of thepresent invention can be cured under inert conditions or as a laminatedstructure.

Commercially available EB-dryers include, for example, those from EnergyScience, Inc. of Wilmington, Mass., or from Advanced Electron Beams Inc.(AEB) of Wilmington, Mass. The energy absorbed, also known as the dose,is measured in units of kilo-Grays (kGy), one kGy being equal to 1,000Joules per kilogram. Typically, the electron beam dose should be withinthe range of 10 kGy to about 40 kGy for complete curing. With theradiation curable composition of the present invention preferably curedby a radiation dose of 20-30 kGy at an oxygen level of <200 ppm isusually sufficient to get a dry, solvent resistant ink.

The present invention has been described in detail, including thepreferred embodiments thereof. However, it will be appreciated thatthose skilled in the art, upon consideration of the present disclosure,may make modifications and/or improvements on this invention that fallwithin the scope and spirit of the invention.

EXAMPLES

The following examples illustrate specific aspects of the presentinvention and are not intended to limit the scope thereof in any respectand should not be so construed.

TABLE 1 Semiconductor Metal Oxide Materials, Additives for Composites,and Composite Formulations ID Grade Source Chemistry Components Zn1NanoArc ® Nanophase Technologies ZnO ZN-2605 Corporation Ti1 P25 Evonik(USA) TiO₂ AC Darco Sigma-Aldrich (USA) Carbon black Ti2 Altiris 550Huntsman TiO₂ Bi1 Sigma-Aldrich (USA) BiOCl Bi2 Alfa Aesar (USA) Bi₂O₃Mg1 Acros Organics (USA) MgO Fe1 Alfa Aesar (USA) Fe₂O₃ NT1 DragoniteAPA Applied Minerals Inc. Aluminosilicate clay nanotubes CompositesPreparation BGA1 TiO₂ and carbon black were Ti1 and AC suspended inwater and sonicated for 2 hr. at 35° C. A color changed from gray toblue grey. The suspension was filtered and dried. BGA2 Ti1, AC, Bi1, Allmaterials were premixed (at equal Bi2, Mg1 weight % of each component),and and Zn1 water was added in a ratio of 0.2 ml of water for every gramof mixed BGA solid. The resulting paste was mixed in a DAC orbital mixeron high speed for 2 min. two times. The complex was then EB pretreatedat 30 ppm oxygen at 50 kGy. BGA3 Ti1, Zn1 Ratio of 3% Ti1, 2% ZN1 and 1%and NT1 NT1 (wt. %) were added to the ink and mixed on a DAC orbitalmixer on high for 2 minutes (twice).

Formulations: Actinic radiation curable inks and coating inks wereprepared by mixing the component(s) from Table 1 into an ink or inkcomponents listed in Table 2 using Flack Tek Inc.'s DAC 400 orbitalmixer for 5 minutes at 1800 rpm.

TABLE 2 Testing Materials: Inks, Ink Components and Substrates IDMaterial Source HDDA 1,6-hexanediol diacrylate Sigma/Aldrich (USA)Black1 SunCure Advance Process Sun Chemical Corp. Black (FLAS9444530) UVlithographic ink Black2 SunCure LO/LE PRO Black Sun Chemical Corp. (UV FSeries E124900267) UV lithographic ink Black3 Plastuff Print Black InkSun Chemical Corp. (FLYCV9344111) UV Dry Offset ink Black4 SunCure MaxDUV flexo black Sun Chemical Corp. ink Cyan1 SunCure Advance Process CyanSun Chemical Corp. (FLASV5444531) UV lithographic ink Cyan2 SunCure UVLED Process Cyan, Sun Chemical Corp. (91540321) UV flexo ink Magenta1SunBeam Magenta EB Sun Chemical Corp. (FLYWB4444136) UV lithographic inkUVC1 UV flexo coating Sun Chemical Corp. (RCSFV0343453) Coated CoatedLeneta, Leneta Company Leneta Form 1A - Penopac Inc., Mahwah NJ UncoatedUncoated Leneta, Leneta Company Leneta Form N2A-3 Inc., Mahwah NJ SBSSolid bleached sulphate Graphic Packaging (SBS) fiber gradeInternational of paperboard White OPP White Oriented Avery DennisonPolypropylene film Corporation PP Cup Polypropylene cups lot BerryGlobal Inc. ZTT21506CP1

Ink preparation: Inks were prepared using a Speed mixer (DAC 150 FVZ) @1 min. 18,000 RPM. 3-roll milling was used as needed and described.

Proofing: Offset and dry offset inks were proofed with a “Little Joe”proofer (Little Joe Industries of Hillsborough, N.J.) with a Warren #2,0.3 mil wedge plate or using an IGT proofer, as specified. Flexo inkswere proofed using a Harper QD Phantom flexo handproofer with a 500 line3.0 BCM anilox roller. Flexo Examples 13-15 were proofed using a HarperJr. handheld proofer with 800 (LPI) line per inch×1.90 (BCM) billioncubic microns using QD proofing bed.

Curing: Curing with exposure to UV light is as described for eachexample. UV-LED cure was achieved at 100 meters/min on GEW UV LED Labunit. EB cure was achieved on a Comet EB BEAM EB Lab-200 at 30 ppmoxygen and dose of 50 kGy at 100 ft/min.

Extent of Cure/Isopropanol Rub Test: Extent of cure was determined bycounting the number of rubs (strokes) it takes a cotton tipped sticksoaked in isopropanol to break through the ink and reveal the underlyingsubstrate. The more rubs it takes to break through, the better the cure.IPA rubs were performed using a Puritan sterile cotton tipped applicator(swab) soaked in IPA and determined by counting the number of rubs(strokes) it takes to break through the ink and reveal the underlyingsubstrate. The higher the number of rubs, the better the IPA rubresistance.

Adhesion and Cure: The adhesion of the ink to substrate (and cure) wasdetermined by applying a 1 inch strip tape (either 3M's 600 & 610 tape)to the cured film by hand and then pulled quickly from the surface. Theestimated % of ink removal is determined by eye. observed % of inkremoval. The lower the % of ink removal, the better the tape adhesion,and the better the cure.

Color Measurements: Black was measured using 3 reflectance metrics(Carbon Blackness [My], Jetness [Mc], and Undertone [dM]). Blackness(My) is a measure of the degree of blackness directly related to thereflectance. Reflectance values are typically below 5% and can be below1% for the best blacks. The bottom-of-scale standardization of theinstrument sets a measured reference for 0%. Where, blackness My=100*log(Yn/Y).

Jetness (Mc) is the color dependent black value developed byLippok-Lohmer (Lippok-Lohmer, K., 1986, Farbe und Lack, 92 11,1024-1029). As the Mc value increases, the jetness of the masstoneincreases. Sample preparation is typically based on an opaque drawdownof a black masstone based on black pigment and binder. Where, jetnessMc=100*[log(Xn/X)−log(Zn/Z)+log(Yn/Y)]. The test sample is typicallymeasured with a directional 45/0 instrument geometry, and Xn=94.811,Yn=100.000, Zn=107.304 are the CIE White Point values for D65/10conditions. X, Y, Z are the CIE tristimulus values for the sample beingmeasured

Undertone (dM) quantifies how neutral the black pigment+binder is. AsMc=dM+My

Where, undertone dM=Mc−My

If dM<0, the undertone is brown-reddish.

A dM value=0 would suggest the black is perfectly achromatic or neutral.

If dM>0, then the black exhibits a bluish undertone which is oftenpreferred.

Alternatively, CIELAB color space may also be implemented. The Lab colorspace is used when graphics for print have to be converted from RGB toCMYK, as the Lab gamut includes both the RGB and CMYK gamut. Also, it isused as an interchange format between different devices as for itsdevice independency. The space itself is a three-dimensional real numberspace, which contains an infinite number of possible representations ofcolors.

However, in practice, the space is usually mapped onto athree-dimensional integer space for device-independent digitalrepresentation, and for these reasons, the L*, a*, and b* values areusually absolute, with a pre-defined range. The lightness, L*,represents the darkest black at L*=0, and the brightest white at L*=100.The color channels, a* and b*, will represent true neutral gray valuesat a*=0 and b*=0. The red/green opponent colors are represented alongthe a* axis, with green at negative a* values and red at positive a*values. The yellow/blue opponent colors are represented along the b*axis, with blue at negative b* values (so that relative values of b thatdecrease mean a bluer undertone), and yellow at positive b* values. Thescaling and limits of the a* and b* axes will depend on the specificimplementation of Lab color. Color measurements and color densityreadings were taken using a SpectroEye, 45:0 spectrodensitometer and theColor iControl program.

Gloss: Measurements were taken using a BYK Gardner micro-TRI-gloss meterat a 60° reflectance angle. Gloss is an aspect of the visual perceptionof objects (i.e. the attribute that causes them to have shiny, metallicor matte appearances). This angle is also the universal measurementangle.

Unless indicated otherwise, all amounts are wt %, based on totalcomposition weights.

Inventive Example 1

BGA1 described in Table 1 above was added to HDDA at 1% wt. UV pulseswere emitted at 0.5 s intervals at wavelengths between 325 nm to 500 nm.A photo-DSC spectrum (TA Instruments, Q2000) was generated and is theFIGURE. As shown, a distinctive heat signature was observed (top curve,the FIGURE) as the HDDA underwent UV-free radical photochemicalpolymerization in the presence of the semiconductor TiO₂ metal oxide. Incontrast, no heat signature is seen when HDDA is exposed to UV lightwithout the semiconductor material being present (lower curve, FIG. 1).This evidences that a polymerization reaction occurs with BGA1composite, with bonds being created and heat being released.

Inventive Example 2

0.5% BGA1 in Cyan1 was proofed with the Little Joe on three substratesand UV cured with an Hg UV lamp at 100 fpm, 200 W/inch and 200 mJ/cm².

TABLE 3 Improved UV Cure with 0.5% BGA1 in Cyan1 as Indicated by IPARubs Cyanl (Comparative) - Ex. 2 (Inventive) - Substrate IPA Rubs IP ARubs Coated 3 6 Leneta Uncoated 4 7 Leneta SBS 4 7.5

Table 3 shows that the addition of 0.5% BGA1 to Cyan1 ink leads to animprovement in the cure of the ink, as indicated by the increase in IPArubs relative to the ink not containing BGA1. It can be seen that theaddition of 0.5% BGA1 increased the IPA rubs by almost twofold.

Inventive Example 3

The photoinitiator content in Black 1 was reduced by 10%, and then 3%Zn1 was added to Black1, which was proofed with a “Little Joe” on SBSand UV cured with an Hg UV lamp at 100 fpm, 200 W/inch and 200 mJ/cm².Black 1 without the addition of Zn1 was proofed and cured in the samemanner to provide a comparison. The photoinitiator concentration wasreduced by 10% from Black1. Table 4 includes the test results.

TABLE 4 Reduced Photoinitiator with Equal UV Cure using 3% Zn1 in Black1Black1 (Comparative) Ex. 3 (Inventive) Photoinitiator Std Reduced by 10%Blackness (My) 154 180 Jetness (Mc) 149 174 60° Gloss 23 29 IPA Rubs 1.22.5

The results in Table 4 are averages calculated from 3 measurements fromeach print, with a total of 3 prints. As shown in Table 4, the additionof 3% semiconductive ZnO metal oxide increased the avg. blackness (My),jetness (Mc) and gloss of the Inventive UV black lithographic ink ofExample 3 in which photoinitiator has been reduced by 10%. Further,inventive Example 3 was more thoroughly and completely cured relative tothe comparative Black 1.

The above demonstrates that the inclusion of semiconductor metal oxidematerials enhances the color of the cured inks, and further, that theinclusion does not adversely affect the cure (in fact, the cure issuperior). Of note is that with the reduction of photoinitiator inBlack1 and replacement of same with Zn1, the color, gloss and number ofIPA rubs are superior to the corresponding comparative example. Further,1 part of Zn1 (1 part) replaces 3.33 parts of photoinitiator, showingthat the replacement amounts of semiconductor metal oxide forphotoinitiator can exceed more than a 1 for 1 exchange of parts.

The inclusion of the semiconductor metal oxide material in an actinicradiation curable ink appears to generate additional free radical curingreactions on exposure to UV light, enhancing cure. Normally, increasesin density in black inks suffer a reduction in cure. Zn1 increased thedensity of the ink and increased the IPA rubs and therefore an increasein cure and color was demonstrated.

Inventive Example 4

9.5% of semiconductive Zn1 metal oxide was added to Black1 was proofedwith a “Little Joe” on SBS board and UV cured. Prints were passed underthe UV cure unit with a Hg UV lamp at 100 fpm, 200 W/inch and 200 mJ/cm²once and twice to simulate light levels the ink would be exposed to on acommercial press where interstation curing is used. Under theseconditions, the inks would see multiple exposures to the UV curingunits. Black 1 without the addition of Zn1 was proofed and cured in thesame manner to provide a comparison.

TABLE 5 Improved UV Cure with 9.5% Zn1 in Black1 Black1 (Comparative)Ex. 4 (Inventive) Blackness (My) 185 197 Jetness (Mc) 182 196 60° Gloss32 35 IPA Rubs - 1^(st) UV Exposure 1 5 IPA Rubs - 2^(nd) UV Exposure 311

As shown in Table 5, the addition of 9.5% of semiconductive ZnO metaloxide to the inventive ink increases the optical properties, such asblackness, jetness and gloss and the cure is greatly enhanced, relativeto the comparative Black 1 that does not include the of semiconductiveZnO metal oxide and which includes the full amount of photoinitiator.

Notably, the addition of the semiconductor metal oxide to inventiveexample 4 reduced the pigment loading thereof. The demonstratedimprovement in color properties and gloss despite containing a lowerproportion of pigment is a surprising result.

Results are averages calculated from 3 measurements from each print,with a total of 3 prints. Table 5 shows that the inclusion ofsemiconductor metal oxide materials can dramatically increase the curewhile improving blackness, jetness and gloss. After one UV exposure thecure improved from 1 to 5 IPA rubs. After the second UV exposure, thecure improved from 3 to 11. Example 4 demonstrates that the inclusion ofa semiconductor metal oxide material interacts with a pigment to createcolor enhancement and at the same time promote photopolymerizationcuring reactions.

Inventive Example 5

5% BGA2 was added to Magenta1 EB lithographic ink was proofed on SBSusing a Little Joe and cured by EB at 30 ppm oxygen and dose of 50 kGy.Magenta1 was proofed onto SBS and cured to provide a comparison.

TABLE 6 Improved EB Cure with 5% BGA2 in Magenta1 Magenta1 (Comparative)Ex. 5 (Inventive) L* 47.8 47.1 a* 72.3 75.8 b* 9.5 5.9 60° Gloss 12.924.5 IPA Rubs 6 44

Table 6 shows that the inclusion of the BGA2 composite (semiconductiveTiO₂, carbon black, semiconductive BiOCl, semiconductive Bi₂O₃, andsemiconductive MgO in equal parts) was both a cure- and color-enhancerfor an electron beam (EB) based ink that does not includephotoinitiator.

Results are averages calculated from 3 measurements from each print,with a total of 3 prints. BGA2 was formed by combining TiO₂, carbonblack, BiOCl, Bi₂O₃, MgO and ZnO and EB pretreated by passing thecomposite into the EB Unit at 30 ppm O₂ at 50 kGy, 24 hr. prior toinclusion into the ink.

The addition of 5% BGA2 to Magenta EB lithographic ink, results in anincrease in the density, and the magenta is bluer (the b* value islowered, giving a bluer undertone), and the cured ink is glossier, allrelative to the comparative ink. In addition to the improved visualproperties, there is a significant increase IPA rubs, (6 to 44), whichis indicative of a deeper and more thorough cure. This demonstrates thatthe composite interacts with the pigment to cause color enhancement andincrease the degree of free radical polymerization curing.

Notably, the addition of the BGA 2 semiconductor metal oxide compositeto inventive example 5 reduced the pigment loading thereof. Thedemonstrated improvement in color properties and gloss despitecontaining a lower proportion of pigment is a surprising result.

Inventive Example 6

2.5% semiconductive ZnO (Zn1) was added to Black2, a UV-curableflexographic ink was proofed onto white oriented polypropylene films(OPP) film and cured with an Hg UV lamp at 100 fpm, 200 W/inch and 200mJ/cm². Black2 was proofed onto OPP and cured to provide a comparison.

TABLE 7 Improved Color Density with 2.5% Zn1 in Black2 Black2(Comparative) Ex. 6 (Inventive) Blackness (My) 177 183 Jetness (Mc) 164171 60° Gloss 49 60 IPA Rubs 1.50 1.50

Table 7 shows that the inclusion of 2.5% Zn1 in an ultraviolet (UV)curable ink enhances the color of the cured ink, and visually apparentincrease in blackness/jetness and gloss occurs in Example 6, allrelative to comparative Black2. This is an example of a semiconductormetal oxide material interacting with pigments present in the ink andcreating color enhancing effects.

Notably, the addition of the Zn1 to inventive example 6 reduced thepigment loading thereof. The demonstrated improvement in colorproperties and gloss despite containing a lower proportion of pigment isa surprising result.

Inventive Example 7: BGA3 in Black3 Dry Offset Inks on Polypropylene(PP)

6% BGA3 (semiconductive TiO2, semiconductive ZnO, and aluminosilicateclay nanotubes) was added to Black3 and three rolled milled. A PPplastic cup was cut into a flat sheet and corona treated using twopasses under an Enercon by passing the substrate through the unit twotimes at 26 fpm and 0.42 kW. Inks were proofed onto the PP using an IGTproofer and cured at 400 watts per inch (wpi) at 200 fpm. Black3 wasproofed onto the same PP substrate and cured to provide a comparison.

TABLE 8 Improved Cure with 6% BGA3 in Black3 Black3 (Comparative) Ex. 7(Inventive) IPA Rubs 18 46 Density 1.65 1.70

Results are averages calculated from 3 measurements from each print,with a total of 3 prints. As shown in Table 8, the inclusion of BGA3more than doubles the IPA rubs, indicating a significant improvement incure. Color density increased as well. This shows that complexes ofsemiconductor metal oxides and clay nanotubes can combine to greatlyimprove the cure of UV inks.

Inventive Example 8: BGA3 in Irgacure 369 Free Vs. Black3 Dry OffsetInks on PP

2.4% Irgacure 369 was removed from Black3 and then 2.4% BGA3 was addedto the ink and mixed into the ink using a DAC mixer. A PP plastic cupwas cut into a flat sheet and corona treated in two passes under anEnercon by passing the substrate through the unit two times at 26 fpmand 0.42 kW. Inks were proofed onto the PP using an IGT and cured at 400wpi at 200 fpm. For comparison, the Black3 ink containing 2.4% Irgacure369 was proofed onto the same PP substrate and cured to provide acomparison.

TABLE 9 Irgacure 369 free inks with 2.4% BGA3 vs. UV Black3 Black 3(Comparative) Ex. 8 (Inventive) IPA Rubs 12 16 Density 1.78 1.77

Results are averages calculated from 3 measurements from each print,with a total of 3 prints. As shown in Table 9, the Irgacure 369-free inkexhibited superior cure and comparable density. This demonstrates thatthe inventive composites significantly improve the cure of UV inks whileadvantageously eliminating undesirable photoinitiators. Irgacure 369cannot be used in food packaging inks because it very toxic to aquaticlife. Studies showing that it is suspected of damaging fertility andharming the unborn.

Inventive Example 9: BGA3 in Irgacure 369 Free Vs. UV Flexo Black4 onPET

UV Flexo Black4 includes 5% Irgacure 369. In inventive example 9, 5%Irgacure 369 was replaced with 5% of BGA3 in UV Flexo Black4. Example 9was proofed using a Harper flexo handproofer onto corona treated PETfilm with a 700 lpi, 2.2 bcm anilox, and cured at 400 wpi and 300 fpmbelt speed. The prints were passed through the cure unit multiple timeswhich replicates what the ink would see on press where the ink/substratepasses under a UV lamp after each print unit. For comparison, the Black4containing 5% Irgacure 369 was proofed onto the same PET substrate andcured to provide a comparison.

TABLE 10 IPA Rubs of Irgacure 369 free inks vs. 5% BGA3 in Black3 Black4 (Comparative) Ex. 9 (Inventive) One UV Pass 11 13 Two UV Passes 36 70

With inventive Example 9, multiple exposure (i.e., 2 UV passes) to theUV energy emitted by the lamps formed cured printed articles exhibitingsignificantly improved cure, as indicated by the increase in the numberof IPA rubs required for removal, relative to Black4. Again, theelimination of Irgacure 369 provides significant benefits.

Inventive Example 10: BGA1 in UV LED vs. Cyan2 on PET

A BGA1 dispersion of 50% in ethoxylated trimethylolpropane triacrylate(EOTMPTA) was prepared by mixing in a DAC mixer. 5% of this mixture wasadded to Cyan2 ink and mixed in a DAC mixer. The ink was proofed using aHarper flexo handproofer onto corona treated PET film with a 700 lpi,2.2 bcm anilox, and cured at 100 fpm with a UV LED cure unit. Cyan2 wasproofed onto the same PET substrate and cured to provide a comparison.

TABLE 11 Cyan2 UV LED Flexo with 5% BGA1 Cyan2 (Comparative) Ex. 10(Inventive) IPA Rubs 11 100+

Inventive Example 11: UV Cure of 5% BGA1 or Bi2 in EOTMPTA

5% BGA1 was added to EOTMPTA. Visible light pulses were emitted at 1.0 sintervals, 5% light intensity for 10 cycles, between 400 nm-500 nm and aphoto-DSC heat emission was measured (TA Instruments, Q2000). The heatsignature for the pan and EOTMPTA were subtracted and the areas underthe curves summed together. The units of mW/g is related to the enthalpyof reaction as bonds are formed, also known as heat of curing. The aboveprocedure was repeated with 5% Bi2 (Bi2O3) replacing the 5% BGA1.Results are given in Table 12.

TABLE 12 Enthalpy of Reaction of BGA1 and Bi2 in EOTMPTA 5% BGA1 in 5%Bi2 in Cycle EOTMPTA mW/g EOTMPTA mW/g 1 45 43 2 30 32 3 27 28 4 26 28 534 32 6 29 29 7 25 24 8 34 31 9 29 26 10 24 23

Distinctive heat signatures for each mixture were observed under visiblelight, indicating free radical photochemical polymerization curingreactions have occurred between the monomers in the presence of thesemiconductive metal oxide materials and the composite. Thisdemonstrates that a reaction is initiated in the monomers in thepresence of BGA1 and Bi2 with visible light exposure. The enthalpy ofreaction values show that bonds are created and heat is released, withno photoinitiators being present. This shows that semiconductor metaloxides are capable of initiating photopolymerization without the needfor a photoinitiator.

Example 12 (Prophetic): Semiconductor Metal Oxide in Adhesive

UV-curable adhesive compositions are formulated with materialscomparable to those used to make inks and coatings. Based on resultspresented, improvement in cure should be possible if semiconductor metaloxide materials are added to the existing photoinitiator package toincrease or some photoinitiators are replaced while maintaining cure.

TABLE 13 Photoinitiator Compound Formulation (82% photoinitiator)Inhibitor 2.0 (2.2 Dihydroxy-4-methoxybenzophenone) propoxylatedneopentyl glycol diacrylate (PONPGDA) 9.0 PPTTAA (AlkoxylatedPentaerythritol Tetraacrylate) monomer 7.0 Irgacure 369 (BASF)photoinitiator 15.0 Irgacure 819 (BASF) photoinitiator 7.0 ethyl4-dimethylaminobenzoate (EDB) photoinitiator 16.0 Chivacure 70 (Chitec)photoinitiator 32.0 Esacure 1 (IGM) photoinitiator 12.0 Total 100.0

TABLE 14 Photoinitiator-Semiconductor Metal Oxide Material CompoundFormulation (64.5% photoinitiator): TiO₂ Atiris 550 10.0 ZnO Zinc oxide10.0 PPTTAA monomer 15.0 Thioxanthone photoinitiator 25.0 Irgacure 819(BASF) photoinitiator 8.0 TPO-L photoinitiator 31.5 Optiblanc PL(optical brightener) 0.5 Total 100.0

Ti2 and Zn1 were formulated into a photoinitiator compound (Table 14).Irgacure 369 was eliminated and the overall concentration ofphotoinitiators was reduced from 85% to under 64%. UV Flexo inks weremade by mixing the photoinitiator compounds in Table 13 and Table 14with Sun Chemical's cyan base (Table 15, yellow base (Table 16) andlithol rubine base (Table 17) and PPTTAA monomer with a Speed Mixer DAC150 FVZ at 1 min at 18,000 rpm.

TABLE 15 Cyan Flexo Ink Examples 13 (Comparative) & 13A (Inventive) Ex.13 Ex. 13A Material (Comp) (Inv.) UV cyan flexo base (Sun Chemical) 5050 PPTTAA 25 25 Table 13 Photoinitiator Compound 25 0 Table 14Photoinitiator Compound 0 25 with Semiconductor metal oxide Total 100100

TABLE 16 Yellow Flexo Ink Examples 14 (Comparative) & 14A (Inventive)Ex. 14 Ex. 14A Material (Comp) (Inv.) UV Yellow flexo base (SunChemical) 50 50 PPTTAA 25 25 Table 13 Photoinitiator Compound 25 0 Table14 Photoinitiator Compound 0 25 with Semiconductor metal oxide Total 100100

TABLE 17 Rubine Flexo Ink Examples 15 (Comparative) & 15A (Inventive)Ex. 15 Ex. 15A Material (Comp) (Inv.) UV Rubine flexo base 50 50 (SunChemical) PPTTAA 25 25 Table 13 Photoinitiator Compound 25 0 Table 14Photoinitiator Compound 0 25 with Semiconductor metal oxide Total 100100

For all sets of ink examples (15/15A; 16/16A; 17/17A) viscositymeasurements were taken using an TA Instruments Rheolyst cone & platerheometer equipped with a 4 cm, 2° steel cone at 25° C. in a strainsweep test and found to be equivalent (±10%) between the Inventive andComparative Examples for each of the 3 sets of inks. Inks were proofedonto an acrylic coated PET film using a Harper Jr. handheld proofer with800 (LPI) line per inch×1.90 (BCM) billion cubic microns using QDproofing bed and cured using an American Ultraviolet UV processor curingunit with a 12-inch width conveyor with belt speeds of 300 (FPM) feetper minute, 400 (WPI) watts per inch 12-inch Hg bulb (mercury vaporpressure) lamp.

TABLE 18 Test Results for Examples 13-15 on Untreated Acrylic coated PETfilm Tape adhesion IPA Color Example 600 610 rubs density Ex. 14 UVflexo free radical 0%  25% 25 0.87 yellow ink Ex. 14A UV flexo freeradical 0% 100% 25 0.90 band gap yellow ink Ex. 15 UV flexo free radical0%  0% 42 2.26 rubine ink Ex. 15A UV flexo free radical 0% 100% 50 2.27band gap rubine ink Ex. 13 UV flexo free radical 0%  0% 1 1.54 cyan inkEx. 13 A UV flexo free radical 0% 100% 34 1.59 band gap cyan ink

The results shown in Table 18 illustrate that the use of Altiris 550(TiO₂) and zinc oxide as semiconductor metal oxide materials in UV flexoHg curable inks of inventive examples 13A, 14A, and 15A exhibitcomparable or better IPA resistance results, superior tape adhesionresults (cure) and improved color density. Notably, the inventiveexamples achieve these results while being free of the toxic IRGACURE®369. Further, the total amount of photoinitiator was reduced in theinventive example.

The present invention has been described in detail, including thepreferred embodiments thereof. However, it will be appreciated thatthose skilled in the art, upon consideration of the present disclosure,may make modifications and/or improvements on this invention that fallwithin the scope and spirit of the invention.

What is claimed is:
 1. A composition curable by exposure to actinicradiation comprising a polymerizable component selected from anethylenically unsaturated monomer, an ethylenically unsaturatedoligomer, an ethylenically unsaturated prepolymer, and combinationsthereof; and a photocatalytic material comprising a semiconductor metaloxide material, optionally present as a composite comprising thesemiconductor metal oxide material or a mixture of semiconductor metaloxide materials, and another composite forming material, wherein thesemiconductor metal oxide component upon exposure to a reaction-startingdose of actinic radiation creates a free radical polymerization reactionpathway in the polymerizable, ethylenically unsaturated componentwithout loss of the semiconductor metal oxide, wherein the semiconductormetal oxide materials and composites thereof can interact directly themonomers, oligomers or polymers.
 2. The composition of claim 1, whereinthe semiconductor metal oxide is as defined in formula (I):M_(x)O_(y)H_(z)  (I) wherein M is a metal selected from Ti, Zn, Mg, Ce,Bi, and Fe; O is oxygen; H is a halogen; x is an integer of 1 to 3; y isan integer of 1 to 3; and z is an integer of 0 to
 3. 3. The compositionof claim 1, wherein the semiconductor metal oxide is present as acomposite, and the another composite forming material is selected frompigments, clays, humic acid, humic acid polymers or optical brighteners.4. The composition of claim 3, wherein the pigments are selected fromcarbon black, halloysite clays, and aluminosilicate clays, litholrubines or combinations thereof.
 5. The composition of claim 1, whereinthe semiconductor metal oxide material is present as a composite, andanother composite forming material of the composite comprises a materialselected from carbon black, aluminosilicate clays, or combinationsthereof.
 6. The composition of claim 1, wherein the semiconductor metaloxide material is present as a composite selected from: a compositecomprising semiconductive TiO₂ and carbon black; a composite comprisingsemiconductive TiO2, semiconductive BiOCl, semiconductive Bi₂O₃, andsemiconductive MgO, and carbon black; a composite comprisingsemiconductive TiO2, semiconductive ZnO, and aluminosilicate clay. 7.The composition of claim 1, wherein the polymerizable componentcomprises an ethylenically unsaturated monomer selected frommonofunctional ethylenically unsaturated monomers and multifunctionalethylenically unsaturated monomers.
 8. The composition of claim 1,wherein the polymerizable component is present in an amount of 10 wt %to 90 wt %.
 9. The composition of claim 1, wherein the polymerizablecomponent comprises an ethylenically unsaturated prepolymer.
 10. Thecomposition of claim 1, wherein the polymerizable component comprises anethylenically unsaturated monomer and an ethylenically unsaturatedprepolymer.
 11. The composition of claim 1, wherein the polymerizablecomponent comprises an ethylenically unsaturated prepolymer selectedfrom epoxyacrylates, acrylated oils, aliphatic urethane acrylates,aromatic urethane acrylates, polyester acrylates, polyether acrylates,vinyl/acrylic oligomers, polyene/thiol systems, or combinations thereof.12. The composition of claim 1, wherein the actinically curablecomposition is a printing ink, coating, adhesive or primer composition.13. The composition of claim 1, further comprising a colorant.
 14. Thecomposition of claim 13, wherein the colorant comprises a pigment. 15.The composition of claim 1, wherein the semiconductor metal oxidematerial or composite thereof is present in an amount of 0.1 wt % to 25wt %.
 16. The composition of claim 1, further comprising aphotoinitiator component comprising one or more photoinitiators.
 17. Thecomposition of claim 16, wherein the photoinitiator component is presentin an amount 2.0 wt % to 40 wt %.
 18. The composition of claim 1,wherein the composition does not include a photoinitiator selected from2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1.
 19. Thecomposition of claim 1, wherein the composition is selected from an ink,a coating, a varnish, or an adhesive.
 20. A method of improving one ormore of cure, color, or color density in an actinic radiation curablecomposition, comprising the steps of providing a printed substrate byprinting the composition of claim 1 onto a substrate and curing theprinted substrate with actinic radiation.
 21. The method of claim 20,wherein the composition further comprises a photoinitiator componentcomprising one or more photoinitiators.
 22. A printed article comprisinga substrate printed with the composition of claim
 1. 23. The printedarticle of claim 22, wherein the substrate is selected from plastics,cellulosics, paper, paperboard or metal.
 24. The printed article ofclaim 22, wherein the substrate is selected from a packaging article, ametal panel, or an electronic article.
 25. A composition curable byexposure to actinic radiation comprising a polymerizable componentselected from an ethylenically unsaturated monomer, an ethylenicallyunsaturated oligomer, an ethylenically unsaturated prepolymer, andcombinations thereof; and a photocatalytic material comprising asemiconductor metal oxide material, present as a composite comprisingthe semiconductor metal oxide photocatalytic material or a mixture ofsemiconductor metal oxide materials, and another composite formingmaterial comprising a material selected from carbon black,aluminosilicate clays, or combinations thereof, wherein thesemiconductor metal oxide upon exposure to a reaction-starting dose ofactinic radiation creates a free radical polymerization reaction pathwayin the polymerizable, ethylenically unsaturated component without lossof the semiconductor metal oxide during the photopolymerization process,wherein the semiconductor metal oxide materials and composites thereofcan interact directly with the monomers, oligomers or polymers.
 26. Thecomposition of claim 25, wherein semiconductor metal oxidephotocatalytic material or mixture of semiconductor metal oxidematerials comprise ZnO, TiO₂, BiOCl, Bi2O₃, MgO or Fe₂O₃.